writeonce/docs/examples/db-bench

db-bench — iteration 22's load generator

The measurement backbone (spec: docs/superpowers/specs/2026-08-21-db-bench-design.md). Pure .wo; every measured mode prints one machine-parsable line per operation class:

<op> <count> <ops/sec> <p50us> <p99us>

Timing is per-operation via time.ticks (CLOCK_MONOTONIC µs). Percentiles come from a 1µs-bucket histogram clamped at 20000µs — exact to the microsecond below the clamp; a p99 AT 20000 means "clamp or worse". (A histogram, not the spec's reservoir: the language has no container element-write or sort, and the histogram's tail fidelity is strictly better. Recorded as a plan deviation.)

Modes

mode	what it prices
all N	the throughput campaign in ONE process: seed N, read N/2, query N/10, write N/2. Without WO_DATA the store is RAM and dies with the process, so the measured modes must share the seeding run.
seed N	timed inserts: one parent per 100 children (FK probe each insert, unique-index maintenance per parent), k non-unique (10 rows/key), deterministic v. Writes Meta expectation rows.
read N	indexed take-1 point lookups, LCG-spread keys.
query N	full equality probes on the k index (≈10 rows each), materialized and counted.
write N	alternating inserts (disjoint k range 2e6+) and updates through query results. Corrupts the checksum by design — durability legs run on a fresh store.
wal N	the crash battery's vehicle: insert-only (k range 1e6+), acked <i> printed AFTER each insert returns — the return IS the ack (RAM applied, WAL record staged, ONE commit done).
verify	store vs its own Meta rows: count, checksum, one unique probe. Exit 3 on mismatch.
verify-acked M	after kill -9 mid-wal: rows 1..M exist with the right v; rows beyond M allowed (acked after the last print flushed). Exit 3 on mismatch.

Coordination idiom (this side of iteration 31)

There is no request/response surface yet: concurrent modes drive completion the db-actor way — actors write rows, main polls the store until the expected count, then settles. Retired when 31 lands.

Standing finding (2026-08-21, first run)

A hand-built multi Bucket of insert results SEGVs on drop: the compiler classifies the elements OWNED while table refs are scalar ids. Query-built multis are runtime-typed and safe. Worked around here (single ref local, bucket-major seeding); the compiler fix is its own slice.